The present invention relates generally to semiconductor fabrication and more specifically to oxynitride etching processes.
The incorporation of oxynitride (e.g. SiON) has proved to provide good integrated circuit (IC) semiconductor device performance. However, high etch selectivity of oxide (e.g. SiO2) to oxynitride is more difficult to achieve than high etch selectivity of oxide to nitride (e.g. SiN).
U.S. Pat. No. 6,063,711 to Chao et al. describes an etch process with a high selectivity of silicon oxide to a silicon oxynitride etch stop.
U.S. Pat. No. 6,074,908 to Huang describes a borderless contact process with an etch stop.
U.S. Pat. No. 6,100,559 to Park describes a graded SiON cap layer that reduces the overall height of a layer stack and provides for increased process control during subsequent patterning of the layer stack.
U.S. Pat. No. 6,214,721 B1 to Bendik, Jr. et al. describes a xe2x80x9cbuilt-inxe2x80x9d wave dampening, antireflective thin-film layer in a copper dual damascene film stack that reduces the standing wave intensity in the deep-UV (DUV) photoresist (PR).
U.S. Pat. No. 4,324,611 to Vogel et al. describes a process and gas mixture for etching silicon dioxide (SiO2)) and/or silicon nitride (SiN) in a plasma environment in a planar reactor.
U.S. Pat. No. 5,302,236 to Tahara et al. describes a method of etching an oxide or nitride film on semiconductor wafer within a processing vessel using a CHF3 etching plasma gas with CO gas present in the plasma atmosphere.
Accordingly, it is an object of an embodiment of the present invention to provide an etch process having an improved oxide to oxynitride selectivity.
Another object of an embodiment of the present invention is to provide an improved method of forming a borderless contact.
Other objects will appear hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a substrate having an exposed conductive structure is provided. An oxynitride etch stop layer is formed over the substrate and the exposed conductive structure. An oxide dielectric layer is formed over the oxynitride etch stop layer. The oxide dielectric layer is etched with an etch process having a high selectivity of oxide-to-oxynitride to form a contact hole therein exposing a portion of the oxynitride etch stop layer over at least a portion of the exposed conductive structure. The etch process not appreciably etching the oxynitride etch stop layer and including: a fluorine containing gas; an inert gas; and a weak oxidant. The exposed portion of the oxynitride etch stop layer over at least a portion of the conductive structure is removed. A borderless contact is formed within the contact hole. The borderless contact being in electrical connection with at least a portion of the conductive structure.